[FEATURE] VPN

[cachebag]

Is your feature request related to a problem? Please describe.

The library only supports WiFi connections. Users cannot connect to VPNs (OpenVPN, WireGuard, IKEv2, etc.) or manage VPN configurations.

Describe the solution you'd like

Add VPN support with an API similar to WiFi:

• list_vpn_connections() - List available VPN connections
• connect_vpn(name: &str, credentials: VpnCredentials) - Connect to VPN
• disconnect_vpn(name: &str) - Disconnect from VPN
• current_vpn() - Get active VPN connection
• forget_vpn(name: &str) - Remove saved VPN

For Developers - what would your solution be?

1. New Models (models.rs):

   • VpnConnection struct with name, type, state
   • VpnType enum (OpenVPN, WireGuard, IKEv2, etc.)
   • VpnCredentials enum with type-specific fields

2. New Module: vpn.rs (internal):

   • Core VPN operations mirroring connection.rs pattern
   • Reuse unified disconnect/state polling logic (after Remove All Repeated “disconnect + wait loop” Logic #79, State polling logic should be unified #80)

3. New Module: vpn_builders.rs:

   • Connection builders for each VPN type (similar to wifi_builders.rs)
   • Start with OpenVPN, expand to WireGuard/IKEv2

4. Update proxies.rs:

   • Add org.freedesktop.NetworkManager.VPN.Connection proxy trait

5. Update network_manager.rs:

   • Add VPN methods delegating to vpn:: module

Dependencies: Should complete #79, #80, #81 first to reuse extracted patterns.

Additional context

VPN connections use virtual interfaces (tun/tap), so device selection differs from WiFi. NetworkManager stores VPN configs in connection.type = "vpn" with type-specific settings in vpn.data dictionary.